1. Field of the Invention
This invention pertains to a transparent high optical quality polyurethane coating layer with self-repairing properties for glass and/or plastic material panes, with this layer being prepared from a reactive mixture containing a plurifunctional, specifically trifunctional, isocyanate component and a plurifunctional polyalcohol component, and possibly a catalyst and other auxiliary substances.
2. Background of the Prior Art
When coating layers of the self-repairing or self-healing anti-lacerative type are applied to silicate glass panes, they serve as anti-shattering coatings, in case the pane is broken, by preventing contact with the sharp edges of the glass fragments. Panes endowed with such coating layers are particularly well-suited for automobile safety windows and are described notably in French patent publications Nos. 2 187 719 and 2 251 608.
Coatings of this type are also known under German patent publications Nos. 2 058 504, 2 634 816, 3 201 849 as coating layers for transparent plastic materials. In this application, these polyurethane layers serve to improve resistance of the plastic materials to scratching and abrasions. These soft polyurethane layers mentioned above in fact have the property of being self-repairing, i.e., superficial imperfections in these layers spontaneously disappear after a short period of time, with the length of time generally depending on the temperature.
These known transparent polyurethane coating layers can be applied to the substratum using various processes. Thus, there is a known method of first producing sheets of this material and applying these sheets to the substratum, while placing a layer of thermoplastic adhesive between them, as described, for example, in French patent No. 2 398 606. There is also a known process of pouring or spraying the reactive mixture forming the polyurethane on the substratum to be coated, after the possible, prior application of an adhesive agent to the substratum.
The aforementioned coating layers have remarkable properties with respect to their resistance to abrasion and scratching, their transparency and their other regular-use properties. However, when they are placed under very humid conditions, atmospheric humidity can condense on their surface, forming very fine droplets of water, which can impede vision through the pane or sheet.
The purpose of the invention is to modify the highly elastic polyurethane coating layers having self-repairing properties as described above, so as to retard or significantly reduce the formation of problem condensation on their surface, in other words, especially to retard the formation of fog while retainingtheir desirable mechanical, optical and general usage properties.